Lock mechanism and alarm



March 17, 1970 P. M. HAWKINS 3,500,670

LOCK MECHANISM AND ALARM Original Filed March 15, 1967 5 Sheets-Sheet 1INVENTOR: 50L M10050 fi Wk/MS P. M. HAWKINS LOCK MECHANISM AND ALARMOriginal Filed March 15, 1967 March 17, 1970 5 Sheets-Sheet 2 March 17,1970 P. M. HAWKINS LOCK MECHANISM AND ALARM Original Filed March 15,1967 5 Sheets-Shefl 5 {20 lEl.E.

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March 17, 1970 P. M. HAWKINS 3,500,570

LOCK MECHANISM AND ALARM Original Filed March 15, 1967 5 Sheets-Sheet 4March 17, 1970 P. M. HAWKINS 3,500,670

LOCK MECHANISM AND ALARM Original Filed March 15, 1967 5 Sheets-Sheet 5I N VEN TOR.

United States Patent 3,500,670 LOCK MECHANISM AND ALARM Paul MaddisonHawkins, Brookville, N.Y., assignor to General Alarm Corporation, NewYork, N.Y., a corporation of Delaware Original application Mar. 15,1967, Ser. No. 623,333, now Patent No. 3,427,413, dated Feb. 11, 1969.Divided and this application Mar. 8, 1968, Ser. No. 729,852

Int. Cl. E05b 17/00, 45/08, 63/14 US. Cl. 70-375 6 Claims ABSTRACT OFTHE DISCLOSURE A lock mechanism employing cylinder means, a plurality ofkey slotted plugs supported for rotation in the cylinder means in tandemdisposition and at least one pin tumbler and driver means associatedwith each plug and the cylinder means normally to maintain same againstrelative rotation but shiftable to a position to permit such rotation;and, if desired, the combination therewith of an alarm actuating switchand means normally maintaining the switch in one position and shiftingsame to a second position upon rotation of one of said plugs.

This invention relates to a lock mechanism, and more particularly, to atamper-proof pin tumbler cylinder lock mechanism with which cooperatingmeans for actuating an alarm upon attempted unauthorized manipulation ofthe mechanism may be associated.

This application is a continuation-in-part of my copending applicationSer. No. 596,840 filed Nov. 25, 1966, now abandoned and a division ofapplication Ser. No. 623,333 filed Mar. 15, 1967, now United StatesPatent No. 3,427,- 413 issued Feb. 11, 1969.

Various types of alarm actuating mechanisms are known wherebyunauthorized entry into a locked premises is sensed and indicated by theoperation of an alarm. However, all too often mechanisms of this typehave been able to be defeated so that the alarm is not actuated upon theoccurrence of an unauthorized entry; and, even where the alarm isactuated, this usually occurs after the entry has taken place. As thesecurity technology has advanced, the development of means to nullifythe improvements has also advanced. Thus, there has been a long standingneed for a tamper-proof lock mechanism which, while operable to permitauthorized entry, resists unauthorized entry and may be combined withmeans to actuate an alarm upon attempted unauthorized entry.

The present invention contemplates a key actuated lock mechanism of theclass described which is exceedingly difficult, if not impossible, tomanipulate without a proper key and which may be associated with alarmactuatin g means so that, if even partially manipulated, it will actuatean alarm.

Accordingly, an important feature of the invention resides in apparatusof the class described comprising: cylinder means, a plurality of keyslotted plugs supported for rotation in the cylinder means in tandemdisposition relatively to one another, and at least one pin tumbler anddriver means associated with each of the plugs and the cylinder meansnormally to maintain the same against relative rotation and shiftable toa position to permit such rotation. It will be understood by thosepersons skilled in the art that the term cylinder means as used herein,comprises separate, aligned cylinders containing one or more plugs, or asingle cylinder containing all the plugs.

In one embodiment of the present invention wherein means to actuate analarm are associated with the cylinder means, there are utilizedcylinder means comprising first and second key actuated pin tumblercylinder and 3,500,670 Patented Mar. 17, 1970 ice key-slotted plugssupported for" rotation therein in tandem disposition relatively to oneanother, an alarm actuating switch, means under the respective controlof the plugs normally maintaining the switch open, and means shiftingthe switch to closed position upon rotation of 'one of the plugs.

The cylinder means, when it comprises several cylinders as in theillustrated embodiment, when disposed in a closure such as a door, willbe in tandem in a line perpendicular to the planes of the inner andouter surfaces of the door so that the cylinders may be regarded asouter and inner cylinders.

The means under the respective control of the plugs may take the form ofa first cam positioned at the rear of the outer plug and rotatabletherewith, and a second cam positioned at the front of the inner plugand rotatable therewith. The switch is equipped with a follower that isspring biased toward the cam surfaces of both cams.

The first cam is contoured normally to maintain the switch in openposition, but to allow the switch to close upon rotation of the outer orfirst plug in either direction.

The second cam is contoured normally to allow the switch to close uponrotation of the first plug from its normal position but to maintain theswitch in open position upon rotation of the second plug.

Thus it will be seen that rotation of the outer or first plug will causethe switch to close, whereas, simultaneous rotation of both plugs willmaintain the switch open.

A bolt operating cam is rotatable with the inner or second plug so thatthe closure cannot be unlocked without rotation of that plug. Authorizedentry, therefore, requires rotation of both plugs and an authorized keyis able to pass through both plugs and cams, the latter having alignedmatching key slots for the purpose, to set the tumblers of both plugsfor rotation.

Thus, if an attempted unauthorized entry is made by picking the lock, ifonly the first or outer plug is picked and rotated, the alarm will beactuated without retraction of the bolt. Should an attempt be made topick both plugs, it would be necessary to pick the second one firstsince only the slightest movement of the first plug alone would actuatethe alarm, and since conventional picking tools used in picking a plugmust be left in the key slot after picking the tumblers of that plug inorder to maintain them in release position While the other plug ispicked. In the event that the inner plug is successfully picked, thepicking tools must remain in the key slot of both plugs so that no roomis left for tools to pick the first plug.

In picking a pin tumbler cylinder plug, as each pin is raised to releaseposition, a rotation force or torque must be exerted on the plug toretain the last picked tumbler in release position until the final oneis picked, at which time, a further torque is necessary to rotate theplug. A further feature of the invention resides in the formation of thelower portion of the key slot of the second plug of a width greater thanthat of the first key slot so that no fulcrum is available in the secondkey slot against which to bear the picking tool to achieve the necessarytorque.

Another feature of the invention contemplates the use of one cylinderplug to prevent unauthorized rotation of the adjacent plug. To this end,the second cam is formed with a recess facing the first cam, and thelatter has a fixed pin extending into the recess. The pin and recess arearranged so that the second plug, if successfully defeated, cannot berotated in a direction to retract the bolt, due to interference of thepin with the side of the recess.

Still further features of the invention reside in formation of theoutermost tumbler and its spool driver of trill resistant material suchas hardened steel so that drill cannot be used to penetrate the tumblersand upport them in release position. The first cam is simiarly formedalso to resist drilling, as is a plate covering he inner end of theinner key slot. This plate may actully be a part of the bolt operatingcam attached to the nner plug.

Additionally, a sleeve surrounding the key slot open- Jgs in the cams isprovided to prevent the injection of uid into the space between the camsto insulate the witch contacts or to harden and prevent movement of hecam follower. This sleeve may be integral with one am and extend into agroove formed in the other cam.

Where the alarm actuating means are not used, if the rst plug only ispicked, nothing happens, i.e. the door annot be opened as the bolt camis still locked. If in ome way additional plugs, and particularly theinner r last plug is picked, the bolt operating cam still canot berotated because of the enlarged portion of the ey slot already referredto, and because the foremost lugs prevent rotation of the tools so thatthese foremost lugs must also be picked, but while the tools for eacharlier picked plug remain in the key slot.

In another embodiment of the invention, I contribute .larm actuatingmechanism comprising: pin tumbler cylider means, a plurality of keyslotted plugs supported 31 rotation therein in tandem dispositionrelatively to me another, two of the plugs having surfaces respectivelyontoured mutually to cooperate to form a recess when 1e two plugs are inselected annular positions respecvely, a follower adapted to engage asurface of the lugs and to be maintained in a first position by thatsurice and to shift into the recess when same is formed pposite thefollower, an alarm actuating switch havingontact means, means normallymaintaining the switch ontact means in a first relative position, andmeans shift- :lg the contact means to a second relative position uponiovementof the follower into the recess.

Actually, the switch may have a pair of contacts and movable insulatingmember mounting one of the conacts, and the insulating member may bemaintained norrally in a position wherein the contacts are in or out felectrical contact, as desired, and may be shiftable uner the influenceof a spring or the like to a position hereby the contacts are out of orin electrical contact hen the follower moves into the recess. For thispurose, the insulating member may have a part bearing gainst thefollower and spring means may urge the inulating member towards thesecond position so that the ontact carried by the insulating membermoves with the IBIllbCI' relatively to the other contact when thefollower hifts. The other contact is preferably biased towards theontact carried by the insulating member when in one f its positions forgood electrical contact. The contacts re, of course, part of an alarmactuating circuit, and for ris purpose one of them may be grounded tothe lock vlinder which may become part of the circuit.

As a feature of this embodiment of the invention, I tilize as a followera ball and I may form the contours n the appropriate plugs so that therecess is frustoconical, r it may be cylindrical and of a depth greaterthan the adius of the ball so that the ball cannot be forced out of 1crecess by turning one of the plugs afterthe alarm is ctuated. Where thealarm actuating means are not used, r should they become inoperative,the follower or ball ill nevertheless fall into its recess if the plugsare picked nd rotated, or if just the first plug is picked and rotated;1d because the recess is dimensioned so that the ball mnot fit entirelyin the recess, the upper part of the all will engage the cylinder andprevent further rotation f the plugs. Utilization of a cylindricalrecess obviates mployment of a rotating force on the plugs, or one ofrem, to force the ball out of the recess. Thus, this armgement, with orwithout the alarm means provides a positive 1 ocking feature againstunauthorized manipulation of the lock.

In another modification of the present invention, the recess isfrustoconical and is formed by a semi-frustoconical contour on each oftwo adjacent plugs, the arrangement being such that when the plugs arein normal position, the follower for which I prefer to use a ball, isspring loaded down into the recess and is dimensioned to be completelycontained within the recess. Thus, an authorized key will not interferewith the ball and can rotate bolh plugs in the cylinder; however, anyattempt to pick either plug, necessarily involves some slight rotationof that plug to maintain the picked pins in unlocking condition, andsuch rotation will cam the ball in a direction out of. the recess, thewalls of which are sufiiciently inclined to achieve that result. Partialprojection of the ball from the recess will cause the ball to interferewith the cylinder thus preventing further rotation of either plug.Additionally, any momentary relaxation of the torque on the picked plugwill permit the ball, acting under the force of its spring to cam theplug back to normal position causing the picked pins to drop back intolocking condition.

There has thus been outlined rather broadly, the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. Those skilled in theart will appreciate that the conception upon which this disclosure isbased may readily be utilized as a basis for the designing of otherstructures for carrying out the several purposes of the invention. It isimportant, therefore, that the claims be regarded as including suchequivalent construction as do not depart from the spirit and scope ofthe invention.

A specific embodiment of the invention has been chosen for purposes ofillustration and description, and is shown in the accompanying drawings,forming a part of the specification wherein:

FIG. 1 is a side elevational view of a lock mechanism according to myinvention;

FIG. 2 is an exploded view illustrating components of the mechanism ofFIG. 1;

FIG. 3 is a side elevational view of an alarm actuating lock mechanismaccording to the present invention;

FIG. 4 is a front elevational view of the mechanism;

FIG. 5 is an elevational section view taken along the lines 5-5 of FIG.3;

FIG. 6 is an elevational section view taken along the lines 66 of FIG.3;

FIG. 7 is a rear elevational view of the mechanism;

FIG. 8 is a side elevational view of another embodiments of an alarmactuating mechanism according to the present invention illustrating samein the normal position;

FIG. 9 is a fragmentary elevational view illustrating parts of themechanism shown in FIG. 8 in alarm actuating position;

FIG. 10 is an end elevational view of the mechanism as shown in FIG. 8partly broken away from purposes of illustration;

FIG. 11 is a view similar to FIG. 10 'but illustrating the mechanism asshown in'FIG. 9;

FIG. 12 is a top plan view of the mechanism of FIGS. 8 to 11;

FIG. 13 is an enlarged perspective view showing the relationship of thefollower in normal position relatively to the recess;

FIG. 14 is similar to FIG. 13, but shows the follower seated in therecess;

FIG. 15 is an elevational view of a further modification of my inventionshowing in dotted outline a portionof the internal construction forclarity; and

FIG. 16 is a front view, partially broken away of the mechanism of FIG.15.

Referring now to the drawings in detail, and more particularly to FIGS.1 and 2 thereof, there is shown a lock mechanism according to thepresent invention and including a cylinder bored longitudinally as at 11for reception in tandem arrangement of key slotted plugs 12, 14 and 15.The front plug 12 is shouldered as at 16 for abutment with the innersurface of a projection 17 on the cylinder facing 19 so that the plugsmust be loaded into the cylinder from the rear and cannot be removedfrom the front end thereof.

A hardened steel spacer 20 is positioned between the cylinder and anescutcheon 21 at the front end thereof to prevent drilling through sameto hold picked pins or drivers in release position.

It will be noted that each of the plugs has one or more vertical bores22 which align with vertical bores in the cylinder 10 in the usual wayto accommodate pin tumblers, drivers and springs for locking each plugagainst rotation relatively to the cylinder. In the presentillustration, the plug 12 is bored to accommodate two pin tumblers, theplug 14 to accommodate three and the plug 15 to accommodate one for atotal of six pins.

An end plate 24 formed with a circular opening 25 is secured by screws26 to the cylinder, and a bolt operating cam 27 is secured by screws 29extending through the opening 25 to the plug 15 for rotation therewithto retract or protract a door bolt, or the like.

Those skilled in the art will appreciate that to open the door withoutan authorized key, the plug 15 must be picked and rotated; 'but to dothis, a torque bearing is required, and as the key slot of this plug isenlarged, as shown at 31, such a bearing is not available unless plugs12 and 14 are also picked. This would be exceedingly dilficult, if notimpossible, since the tools needed to maintain picked plugs in pickedcondition, would interfere with those needed to pick the remainingplugs. Additionally, picking is rendered difiicult because if one plugis picked, it is rotated slightly to maintain the pins in pickedcondition. Thus the area of the key slot is reduced, and will be furtherreduced as the next plug is picked and rotated so that the working areabecomes impossibly small. Meanwhile, should any vibration or slightturning force counterrotate any of the picked plugs, its pins will fallback into locking position.

By way of example, in the arrangement illustrated in FIGS. 1 and 2, thefirst driver may be of hardened steel and of the straight type, whilethe remaining drivers may be of brass, the second and fourth being ofthe mushroom type while the third, fifth and sixth are straight drivers.The first pin tumbler may also be hardened steel and all the rest may beof brass.

Turning now to FIGS. 3 to 7, and particularly to FIG. 3, there is shownan alarm actuating mechanism having a face plate 40 integral with acylinder 41 extending rearwardly thereof. A bore 43 extends through theplate 40 and cylinder 41 for supporting a rotatable plug 44 (FIGS. 3 and4) bored as at 45 for reception of tumbler pins 46 backed by spooldrivers 47 and springs 49 positioned in corresponding bores 50 in thecylinder 41. Only one tumbler pin, driver and spring are shown.

A second cylinder 51 extends rearwardly of and in tandem dispositionwith the cylinder 41, to which it is secured by screws 53, and is boredas at 52 for supporting a rotatable plug 54 bored as at 55 for receptionof tumbler pins 46 backed by spool drivers 47 and springs 49 positionedin corresponding bores in the cylinder 51.

A cam 61 is secured as by screws 62 to the inner or rear face of theplug 44, and the key slot 64 continues through the cam, as shown in FIG.5. This cam 61 has a circular cam surface 65 formed with two adjacentreversecurved depressions 66 separated by a rise or high point 67positioned at the top of the cam when same is in normal position, aswhen the closure is locked.

A second cam 69 is secured as by screws 68 to the outer face of thesecond plug 54, and the key slot 64 continues on through this cam andthe second plug. As shown in FIG. 6, this cam 69 has a circular camsurface 70 formed with a reverse-curved depression 71 which ispositioned at the top of the cam when same is in normal position, aswhen the closure is locked.

Referring now to FIGS. 3 and 7, it will be seen that a bolt operatingcam 72 is fixed to the end of the plug 54 for rotation therewith toprotract and retract the closure bolt (not shown) upon rotation of theplug 54.

A switch 75 (FIGS. 3 and 6) is positioned between the cylinders 41 and51 above the earns 61 and 69 and is equipped with a follower wheel orrollers 76 biased downwardly to switch closing position by a flat spring77 (FIG. 6).

From the description thus far, it will be seen that when the mechanismis in its normal locking position, the follower 76 is prevented frommoving downwardly to switch closing or alarm actuating position by thehigh point 67 of the first cam 61. However, rotation of that cam ineither direction after setting the tumblers of the first cy1 inder torelease position and rotating the plug 44, will allow the switch spring77 to urge the follower 76 into one of the recesses 66 of the first cam,as well as into the recess 71 of the second cam, thus to activate theswitch and the alarm.

On the other hand, when both plugs 44 and 54 are rotated, the high point67 of the cam 61, is shifted away from normal position, but the recess71 of the cam 69 is also shifted from normal position so that thesurface 70 of the second cam maintains the follower in switch closingposition. An authorized key 78 therefore, is of a length to pass throughboth plugs and cams and is bitted to move all the tumblers of bothcylinders to release position.

As stated, an attempt to pick the first cylinder results in actuation ofthe alarm without rotating the bolt cam 72 so that the closure boltremains in locked position. An attempt to pick the second cylinder willbe defeated because of the oversize keyway 73 of the lower part of thesecond plug key slot (-FIG. 6) eliminating the possibility of a torquebearing. Additionally, should the second cylinder tumblers be set torelease position, the tools in the key slot will prevent access to thefirst plug key slot for picking the tumblers of that cylinder. If thetools are removed from the second key slot, at least the last pickedtumbler in the second plug will fall to locking position so that theplug cannot be rotated.

As has been stated, an additional security measure resides in theutilization of one plug to prevent unauthorized rotation of the other.For this purpose, the first cam 61 is provided with an integral pin 82(FIGS. 3 and 5) extending towards the cam 69 which is formed with anarcuate recess 84 (FIGS. 3 and 6) receiving the pin 82. The pin andrecess are so arranged that the inner plug 54 cannot be rotated in adirection to cause the cam 72 to retract the bolt unless the plug 44 isalso free to rotate. Thus, if

the plug 54 is in some way defeated, it still cannot be rotated tounbolt the door without also defeating the first plug 44.

A sleeve 80, which may be integral with the face of one cam, say cam 61for example, extends into a recess 81 formed in the adjacent face of thecam 69 and surrounds the key opening of both cams so that nodebilitating fluid may be injected into the space between the cams tointerfere with the functioning of the cam follower or the switch action.

By hardening the first tumbler and driver of the first cylinder and thefirst cylinder cam 61, the cylinder may not be drilled to provide accessto picked tumblers of the device to support same in release position.

Referring now to FIGS. 8 to 14, and initially to FIG. 8, there is shownanother embodiment of the alarm actuating mechanism which includes acylinder bored longitudinally as at 91 for reception in tandemarrangement of key slotted plugs 92 and 94, although additional plugsmay be employed. The front plug 92 is shouldered as at for abutment withthe inner surface of a cooperating lhoulder 96 on the cylinderescutcheon 97 so that the lugs can only be loaded or unloaded relativelyto the :ylinder from the rear.

A hardened steel spacer 99 is positioned between the :ylinder and itsescutcheon to prevent drilling through tame for the purpose alreadymentioned in respect of the :mbodiment of FIGS. 1 and 2.

It will be noted that each of the plugs 92 and 94 has leveral verticalbores 100 which align with vertical bores l01 in the cylinder in theusual way to accommodate pin Lumblers, drivers and springs for lockingeach plug against 'otation relatively to the cylinder. In the presentillustraion, plug 92 is bored to accommodate three pin tumblers and plug94 is bored to accommodate two pin tumblers :or a total of five suchpins, although any desired number nay be used in each plug.

An end plate 103 formed with a circular opening is iecured by screws 102to the cylinder and a bolt operating :am 104 is secured by screws 105 tothe plug 94 for rozation there-with to retract or protract a door bolt,or the ike.

The difficulties in attempting to manipulate the lock nechanism byunauthorized means have been explained n connection with the embodimentsillustrated heretofore and need not be repeated here.

The alarm actuating mechanism of the present embodinent concerns aswitch and means for shifting the switch from normal, non-alarmactuating condition to alarm actuating condition upon attemptedunauthorized manipuation of the lock mechanism.

Thus, in the present illustration, the switch includes a :ontact 106positioned in a horizontal bore 107 entering he cylinder 90 from itsrear surface and lined with an .nsulating sleeve 109. A compressionspring 110 urges the :ontact 106 to the right, as viewed in FIGS. 8 and9, and :his contact is wired as at 111 to an alarm (not shown).

Another contact 112 is shown as a circular disc, best teen in FIGS. and11, mounted in a segment 115 posizioned in a segmental slot or keyway113 in the cylinder. The segment 115 is formed of insulating materialand has 1 leg or extension 116 projecting from the lower part of )needge thereof into a vertical bore 117 formed in the :ylinder 90 andpositioned so that its longitudinal axis lies .n a plane passing betweenthe plugs 92 and 94. The lower surface of the extension 116 is contouredto engage a ball [19, also in the bore 117, and its upper surface isfiat to seat a compression spring 120, the other end of which bearsagainst a set screw 121.

The adjacent regions of the plugs 92 and 94 are con- :oured so that whenthey are in certain predetermined relative annular positions, the ball119 and segment 115 will move downwardly, as viewed, thus to separatethe :ontacts 106 and 112 to activate the alarm. For this purpose, Ichoose to form a semi-frustoconical configura- ;ion 124 in the plug 94opening towards the plug 92 and iymmetrical about a vertical planethrough the longitudi- Jal axis of the plug when same is in its normalposition as when the bolt 104 is in door locking position. The apposedface of the plug 92 is formed with two similar :onfigurations 125 and126 spaced slightly to each side of a vertical plane through thelongitudinal axis of that plug when in normal position so that theseconfigurations Jverlap, but do not mate with, the semifrustoconical:onfiguration 124 when the plugs are in normal position, or in anyposition achieved by rotation of an author- 'uzed key since suchrotation will rotate both plugs simultaneously and thus maintain theplugs in a constant relative position.

It will be appreciated that, when in normal position. the surface of theplug 92 between the configurations 125 and 126 is positioned directlybelow the ball 119 and maintains same, and therefore the segment 115 inposition to establish electrical contact between contacts 106 and 112;and that in the event of rotaion of the plugs 92 8 and 94 by auhorizedmeans, the surfaces of both plugs will cooperate to maintain thiscondition.

However, in the event that the plug 92 is itself picked or rotated, oneof the configurations 125 or 126, depending upon the direction ofrotation, will come into mating relation with the configuration 124 toform a frustoconical recess beneath the ball 119 which will be drivendownwardly into the recess while the segment also shifts downwardly bythe action of the spring thus to separate the contacts 106 and 112 andactivate the alarm notwithstanding that the door bolt is still inlocking condition.

As shown in FIG. 8, the opposed faces of the plugs 92 and 94 are alsoformed with semi-frustoconical configurations 127 and 129, respectively,so arranged that when the plugs are in normal position, theseconfigurations are in mating relation to present a frustoconical recessat the bottom of the plugs and symmetrical about planes through thelongitudinal axes of the plugs and passing between the plugs. In theevent that an unauthorized person, in some way manages to rotate bothplugs simultaneously, the ball 119 will fall into the lastmentionedrecess when the plugs have been rotated 180 and prior to retraction ofthe door bolt, at which point the alarm will be actuated.

When an authorized key 130 is inserted into the plugs through therespective key slots, the lower region of the key fills the majorportion of the recess formed by configurations 127, 129 so that the ball119 cannot fall into the recess as it passes the 180 position ofrotation, and continued rotation and bolt retraction can occur withoutinterfering with the alarm circuit.

It will be appreciated that once the ball falls into a recess, continuedrotation of the plugs is not possible because, as shown in FIG. 9, theball projects upwardly beyond the exterior surface of the plugs, andsince the cylinder itself would interfere with rotation of the ball, theball in turn interferes with further rotation of the plugs.

If desired, the recesses can be made cylindrical in shape and preferablyof a depth slightly greater than the radius of the ball.

In a further modification of my invention, as illustrated in FIGS. 15and 16, I provide the usual cylinder with escutcheon 136, front plug 137and rear plug 138 to which is secured door bolt operating cam 140, allof which is similar to those constructions already described. Both plugs137 and 138 are groovd eat 141 for reception of two pin tumblers, andeach has a semi-frustoconical configuration 142 on their adjacent faceswhich cooperate to form a recess for reception of a ball 144, the latt rbeing dimensioned so that it is normally fully contained in the recess.A cylindrical slug in bore 143 bears against the ball 144 and has aguide stem 146 extending upwardly thrOugh the coils of a helical spring147 which urges the ball into the recess.

It will be seen that since the ball is fully contained within therecess, an authorized key will simply rotate both plugs and the ball,the latter moving along in engagement with the cylinder wall 149 whenmoved out of its normal position. However, should an attempt be made topick this lock, it would be necessary slightly to rotate the first plugpicked in order to allow the picked pins to rest on the outer surface ofthe plug while others were picked. This rotation of one plug cams theball, through the action of the inclined surface of the recess, againstthe force of the spring, into a position of partial projection out ofthe recess. In such position, the ball cannot rotate because ofinterference wih the cylinder and therefore positively locks the plugsagainst further rotation. Furthermore, if the torque exerted on thepicked plug is relaxed, even for an instant, the spring 147 drives theball downwardly to bear against the wall of the appropriateconfiguration 142 to cam that plug back to normal position at whichposition all the picked pins would drop back into locking condition.

From the foregoing description, it will be seen that the presentinvention provides a novel lock mechanism which is tamper-proof anddrill-proof and which may be employed with alarm actuating means so thatif even partially manipulated, an alarm will be actuated. Whileproviding these advantageous characteristics, the lock may be operatedby an authorized user in the normal way without actuating the alarm. Itwillalso be seen that the present mechanism cannot be defeated bytwisting the outer cylinder, as is sometimes done to conventionalcylinder locks, since as shown in the embodiment of FIGS. 3 to 7 hereindescribed, the torque would shear the screws 53 causing the cylinder 41to rotate to actuate the alarm while the bolt remains locked by thesecond cylinder 51. The screws 53 are of a shear strength to assure thisresult. It will be understood that while the switch 77 has been referredto as normally open for purposes of convenience, it may be normallyclosed and shift to open position to actuate an alarm circuit.

It is believed that the construction and operaion of the novel mechanismherein described will now be understood and that the advantages of theinvention will be fully appreciated by those persons skilled in the art.

I claim:

1. Mechanism of the class described comprising: pin tumbler cylindermeans, a plurality of key slotted plugs supported for rotation thereinin tandem disposition relatively to one another, two of said plugshaving surfaces respectively contoured mutually to cooperate to form arecess when said plugs are in selected annular positions respectively, afollower normally engaging the surface of at least one of said plugs andshifting into said recess when same is formed opposite said follower byrotation of at least one of said plugs into said respective selectedannular positions, and means urging said follower into said recess thusformed opposite said follower.

2. Mechanism according to claim 1 wherein said follower is of adimension to extend out of said recess when seated therein whereby theprojecting portion thereof engages said cylinder means to preventfurther rotation of either of said plugs.

3. Mechanism according to claim 2, wherein said recess is cylindrical.

4. Mechanism of the class described comprising: pin tumbler cylindermeans, a plurality of key slotted plugs supported for rotation thereinin tandem disposition relatively to one another, two of said plugshaving surfaces respectively contoured mutually to cooperate to form arecess when said plugs are in selected annular positions respectively, afollower normally positioned in said recess, said follower and recesscooperating to shift said follower partially out of said recess uponrotation of one of said plugs relatively to the other whereby saidfollower engages the cylinder means to lock said plugs against furtherrotation.

5. Mechanism according to claim 4, wherein said recess is frustoconicaland said follower is spheroid.

6. Mechanism of the class described comprising: pin

tumbler cylinder means, a plurality of key slotted plugs supported forrotation therein in tandem disposition relatively to one another, two ofsaid plugs having surfaces respectively contoured mutually to cooperateto form a frustoconical recess when said plugs are in selected annularpositions respectively, a spheroid follower normally positioned in saidrecess, said follower and recess cooperating to shift said followerpartially out of said recess upon rotation of one of said plugsrelatively to the other whereby said follower engages the cylinder meansto locksaid plugs against further rotation, and spring means biasingsaid follower into said recess, the spring force acting through saidfollower on the recess walls urging said plugs into said selectedannular positions.

References Cited UNITED STATES PATENTS 1,755,847 4/1930 Stevens 3641,990,794 2/1935 McCo'rmac 70368 2,101,779 12/1937 Kenney 703643,385,086 5/1968 Patriquim 70364 RICHARD E. MOORE, Primary ExaminerROBERT L. WOLFE, Assistant Examiner US. Cl. X.R.

